F.4 數學題 ( 急! )

計唔到 唔該幫我計一計 thz!!

1. find the values of k.

{ x^2 - 4y^2 + 20 = 0
{ x + 3y + k = 0

2. solve the following equations.

　3x - 開方2x+1 = 9 <-- (成個 2x+1 開方)

3. solve the following simultaneous equations using the algebraic method.

{ x^2 + y - x = 1
{ 2x + 3y = 1




answers :
1. k = +5 or -5
2. x = 4
3. ( -1/3 , 5/9 ) , ( 2 , -1 )

thank you !